This invention generally relates to refrigeration machines, and more specifically to insuring that a refrigeration machine is properly charged.
As is well understood by those skilled in the art, it is highly desirable that a refrigeration machine be properly charged; that is, provided with the correct amount of refrigerant fluid. For example, if a refrigeration machine is undercharged, the machine may not be able to produce the desired cooling effect. On the other hand, if a refrigeration machine is overcharged, liquid refrigerant may enter the compressor of the machine, adversely affecting the performance thereof and possibly causing damage to the compressor. Consequently, refrigeration machines are often provided with means or apparatus to monitor or to check the charge of the machine.
Insuring that a refrigeration machine has the correct charge is particularly important if the machine includes an expansion device of the fixed size orifice type, for example a capillary tube. Such expansion devices, although relatively simple and inexpensive, operate with maximum efficiency within a comparatively narrow range of temperatures and pressures determined by the system design and charge. Heretofore, however, providing a refrigeration machine having a fixed size orifice type of expansion device with means to monitor the charge of the machine has been complicated by the fact that often such machines do not have a liquid refrigerant collection vessel located between the condenser and the expansion device of the machine, thus rendering inapplicable the many prior art charge checking methods and appartus which employ such a collection vessel.
As a result, prior art arrangements for monitoring the charge of refrigeration machines of the general type described above have been somewhat complex, elaborate, or expensive. For example, these prior art arrangements may require a special operating cycle of the refrigeration machine or that the machine temporarily shut down. These actions may adversely affect machine performance or temporarily render the machine ineffective for its intended purpose. Alternately, these methods and apparatus may require sensing or examining refrigerant fluid conditions in the area of the evaporator of the machine, an area which is often relatively inaccessible or remote. Other prior art charge checking methods and apparatus may require sensing the refrigerant pressure or temperature at a plurality of locations, requiring a considerable amount of hardware such as sensors, tubes, and gauges.